An ion beam etching (hereinafter, also abbreviated as IBE) technique has been widely used for processing a semiconductor memory, a recording device, a magnetic head, and the like (for example, Patent Document 1). The IBE technique forms plasma by inputting power to an electric discharge unit, and then forms an ion beam by extracting ions from the plasma with application of a voltage to a grid. The ion beam is made incident on a substrate, and mainly-physically etches a material on the substrate.